Enhance to handle both Elf32 and Elf64, and little/big endian.

http://buildroot.uclibc.org/cgi-bin/viewcvs.cgi/trunk/buildroot/toolchain/sstrip/sstrip.c Revision 11028 [Added Tue Aug 2 18:20:34 2005 PDT (3 months, 1 week ago) by mjn3] committer: jreiser <jreiser> 1131566192 +0000
2005-11-09 19:56:32 +00:00
parent 910e18fb22
commit 414a6c1c9e
1 changed files with 405 additions and 253 deletions
@@ -1,5 +1,55 @@
+/* http://www.muppetlabs.com/~breadbox/software/elfkickers.html */
+
 /* sstrip: Copyright (C) 1999-2001 by Brian Raiter, under the GNU
 * General Public License. No warranty. See COPYING for details.
+ *
+ * Aug 23, 2004 Hacked by Manuel Novoa III <mjn3@codepoet.org> to
+ * handle targets of different endianness and/or elf class, making
+ * it more useful in a cross-devel environment.
+ */
+
+/* ============== original README ===================
+ *
+ * sstrip is a small utility that removes the contents at the end of an
+ * ELF file that are not part of the program's memory image.
+ * 
+ * Most ELF executables are built with both a program header table and a
+ * section header table. However, only the former is required in order
+ * for the OS to load, link and execute a program. sstrip attempts to
+ * extract the ELF header, the program header table, and its contents,
+ * leaving everything else in the bit bucket. It can only remove parts of
+ * the file that occur at the end, after the parts to be saved. However,
+ * this almost always includes the section header table, and occasionally
+ * a few random sections that are not used when running a program.
+ * 
+ * It should be noted that the GNU bfd library is (understandably)
+ * dependent on the section header table as an index to the file's
+ * contents. Thus, an executable file that has no section header table
+ * cannot be used with gdb, objdump, or any other program based upon the
+ * bfd library, at all. In fact, the program will not even recognize the
+ * file as a valid executable. (This limitation is noted in the source
+ * code comments for bfd, and is marked "FIXME", so this may change at
+ * some future date. However, I would imagine that it is a pretty
+ * low-priority item, as executables without a section header table are
+ * rare in the extreme.) This probably also explains why strip doesn't
+ * offer the option to do this.
+ * 
+ * Shared library files may also have their section header table removed.
+ * Such a library will still function; however, it will no longer be
+ * possible for a compiler to link a new program against it.
+ * 
+ * As an added bonus, sstrip also tries to removes trailing zero bytes
+ * from the end of the file. (This normally cannot be done with an
+ * executable that has a section header table.)
+ * 
+ * sstrip is a very simplistic program. It depends upon the common
+ * practice of putting the parts of the file that contribute to the
+ * memory image at the front, and the remaining material at the end. This
+ * permits it to discard the latter material without affecting file
+ * offsets and memory addresses in what remains. Of course, the ELF
+ * standard permits files to be organized in almost any order, so if a
+ * pathological linker decided to put its section headers at the top,
+ * sstrip would be useless on such executables.
 */

 #include	<stdio.h>
@@ -9,28 +59,14 @@
 #include	<unistd.h>
 #include	<fcntl.h>
 #include	<elf.h>
-#undef EM_X8664
-#define EM_X8664 EM_X86_64
-#include <asm/types.h>
-#undef u32
-#define u32 __u32
-#undef u64
-#define u64 __u64
-#include <asm/elf.h>
+#include	<endian.h>
+#include	<byteswap.h>

 #ifndef TRUE
 #define	TRUE		1
 #define	FALSE		0
 #endif

-#if ELF_CLASS == ELFCLASS32
-#define Elf_Ehdr        Elf32_Ehdr
-#define Elf_Phdr        Elf32_Phdr
-#else
-#define Elf_Ehdr        Elf64_Ehdr
-#define Elf_Phdr        Elf64_Phdr
-#endif
-
 /* The name of the program.
 */
 static char const	*progname;
@@ -49,19 +85,237 @@ static int err(char const *errmsg)
 	return FALSE;
 }

+/* A flag to signal the need for endian reversal.
+ */
+static int do_reverse_endian;
+
+/* Get a value from the elf header, compensating for endianness.
+ */
+#define EGET(X) \
+	(__extension__ ({ \
+		uint64_t __res; \
+		if (!do_reverse_endian) { \
+			__res = (X); \
+		} else if (sizeof(X) == 1) { \
+			__res = (X); \
+		} else if (sizeof(X) == 2) { \
+			__res = bswap_16((X)); \
+		} else if (sizeof(X) == 4) { \
+			__res = bswap_32((X)); \
+		} else if (sizeof(X) == 8) { \
+			__res = bswap_64((X)); \
+		} else { \
+			fprintf(stderr, "%s: %s: EGET failed for size %d\n", \
+					progname, filename, sizeof(X)); \
+			exit(EXIT_FAILURE); \
+		} \
+		__res; \
+	}))
+
+/* Set a value 'Y' in the elf header to 'X', compensating for endianness.
+ */
+#define ESET(Y,X) \
+		do if (!do_reverse_endian) { \
+			Y = (X); \
+		} else if (sizeof(Y) == 1) { \
+			Y = (X); \
+		} else if (sizeof(Y) == 2) { \
+			Y = bswap_16((uint16_t)(X)); \
+		} else if (sizeof(Y) == 4) { \
+			Y = bswap_32((uint32_t)(X)); \
+		} else if (sizeof(Y) == 8) { \
+			Y = bswap_64((uint64_t)(X)); \
+		} else { \
+			fprintf(stderr, "%s: %s: ESET failed for size %d\n", \
+					progname, filename, sizeof(Y)); \
+			exit(EXIT_FAILURE); \
+		} while (0)
+
+
 /* A macro for I/O errors: The given error message is used only when
 * errno is not set.
 */
 #define	ferr(msg)	(err(errno ? strerror(errno) : (msg)))

-/* readelfheader() reads the ELF header into our global variable, and
- * checks to make sure that this is in fact a file that we should be
- * munging.
+
+
+#define HEADER_FUNCTIONS(CLASS) \
+ \
+/* readelfheader() reads the ELF header into our global variable, and \
+ * checks to make sure that this is in fact a file that we should be \
+ * munging. \
+ */ \
+static int readelfheader ## CLASS (int fd, Elf ## CLASS ## _Ehdr *ehdr) \
+{ \
+	 if (read(fd, ((char *)ehdr)+EI_NIDENT, sizeof(*ehdr) - EI_NIDENT) \
+		!= sizeof(*ehdr) - EI_NIDENT) \
+		return ferr("missing or incomplete ELF header."); \
+ \
+	/* Verify the sizes of the ELF header and the program segment \
+	 * header table entries. \
+	 */ \
+	if (EGET(ehdr->e_ehsize) != sizeof(Elf ## CLASS ## _Ehdr)) \
+		return err("unrecognized ELF header size."); \
+	if (EGET(ehdr->e_phentsize) != sizeof(Elf ## CLASS ## _Phdr)) \
+		return err("unrecognized program segment header size."); \
+ \
+	/* Finally, check the file type. \
+	 */ \
+	if (EGET(ehdr->e_type) != ET_EXEC && EGET(ehdr->e_type) != ET_DYN) \
+		return err("not an executable or shared-object library."); \
+ \
+	return TRUE; \
+} \
+ \
+/* readphdrtable() loads the program segment header table into memory. \
+ */ \
+static int readphdrtable ## CLASS (int fd, Elf ## CLASS ## _Ehdr const *ehdr, \
+								   Elf ## CLASS ## _Phdr **phdrs) \
+{ \
+	size_t	size; \
+ \
+	if (!EGET(ehdr->e_phoff) || !EGET(ehdr->e_phnum) \
+)		return err("ELF file has no program header table."); \
+ \
+	size = EGET(ehdr->e_phnum) * sizeof **phdrs; \
+	if (!(*phdrs = malloc(size))) \
+		return err("Out of memory!"); \
+ \
+	errno = 0; \
+	if (read(fd, *phdrs, size) != (ssize_t)size) \
+		return ferr("missing or incomplete program segment header table."); \
+ \
+	return TRUE; \
+} \
+ \
+/* getmemorysize() determines the offset of the last byte of the file \
+ * that is referenced by an entry in the program segment header table. \
+ * (Anything in the file after that point is not used when the program \
+ * is executing, and thus can be safely discarded.) \
+ */ \
+static int getmemorysize ## CLASS (Elf ## CLASS ## _Ehdr const *ehdr, \
+								   Elf ## CLASS ## _Phdr const *phdrs, \
+						 unsigned long *newsize) \
+{ \
+	Elf ## CLASS ## _Phdr const   *phdr; \
+	unsigned long	size, n; \
+	int			i; \
+ \
+	/* Start by setting the size to include the ELF header and the \
+	 * complete program segment header table. \
+	 */ \
+	size = EGET(ehdr->e_phoff) + EGET(ehdr->e_phnum) * sizeof *phdrs; \
+	if (size < sizeof *ehdr) \
+		size = sizeof *ehdr; \
+ \
+	/* Then keep extending the size to include whatever data the \
+	 * program segment header table references. \
+	 */ \
+	for (i = 0, phdr = phdrs ; i < EGET(ehdr->e_phnum) ; ++i, ++phdr) { \
+		if (EGET(phdr->p_type) != PT_NULL) { \
+			n = EGET(phdr->p_offset) + EGET(phdr->p_filesz); \
+			if (n > size) \
+				size = n; \
+		} \
+	} \
+ \
+	*newsize = size; \
+	return TRUE; \
+} \
+ \
+/* modifyheaders() removes references to the section header table if \
+ * it was stripped, and reduces program header table entries that \
+ * included truncated bytes at the end of the file. \
+ */ \
+static int modifyheaders ## CLASS (Elf ## CLASS ## _Ehdr *ehdr, \
+								   Elf ## CLASS ## _Phdr *phdrs, \
+								   unsigned long newsize) \
+{ \
+	Elf ## CLASS ## _Phdr *phdr; \
+	int		i; \
+ \
+	/* If the section header table is gone, then remove all references \
+	 * to it in the ELF header. \
+	 */ \
+	if (EGET(ehdr->e_shoff) >= newsize) { \
+		ESET(ehdr->e_shoff,0); \
+		ESET(ehdr->e_shnum,0); \
+		ESET(ehdr->e_shentsize,0); \
+		ESET(ehdr->e_shstrndx,0); \
+	} \
+ \
+	/* The program adjusts the file size of any segment that was \
+	 * truncated. The case of a segment being completely stripped out \
+	 * is handled separately. \
+	 */ \
+	for (i = 0, phdr = phdrs ; i < EGET(ehdr->e_phnum) ; ++i, ++phdr) { \
+		if (EGET(phdr->p_offset) >= newsize) { \
+			ESET(phdr->p_offset,newsize); \
+			ESET(phdr->p_filesz,0); \
+		} else if (EGET(phdr->p_offset) + EGET(phdr->p_filesz) > newsize) { \
+			newsize -= EGET(phdr->p_offset); \
+			ESET(phdr->p_filesz, newsize); \
+		} \
+	} \
+ \
+	return TRUE; \
+} \
+ \
+/* commitchanges() writes the new headers back to the original file \
+ * and sets the file to its new size. \
+ */ \
+static int commitchanges ## CLASS (int fd, Elf ## CLASS ## _Ehdr const *ehdr, \
+								   Elf ## CLASS ## _Phdr *phdrs, \
+								   unsigned long newsize) \
+{ \
+	size_t	n; \
+ \
+	/* Save the changes to the ELF header, if any. \
+	 */ \
+	if (lseek(fd, 0, SEEK_SET)) \
+		return ferr("could not rewind file"); \
+	errno = 0; \
+	if (write(fd, ehdr, sizeof *ehdr) != sizeof *ehdr) \
+		return err("could not modify file"); \
+ \
+	/* Save the changes to the program segment header table, if any. \
+	 */ \
+	if (lseek(fd, EGET(ehdr->e_phoff), SEEK_SET) == (off_t)-1) { \
+		err("could not seek in file."); \
+		goto warning; \
+	} \
+	n = EGET(ehdr->e_phnum) * sizeof *phdrs; \
+	if (write(fd, phdrs, n) != (ssize_t)n) { \
+		err("could not write to file"); \
+		goto warning; \
+	} \
+ \
+	/* Eleventh-hour sanity check: don't truncate before the end of \
+	 * the program segment header table. \
+	 */ \
+	if (newsize < EGET(ehdr->e_phoff) + n) \
+		newsize = EGET(ehdr->e_phoff) + n; \
+ \
+	/* Chop off the end of the file. \
+	 */ \
+	if (ftruncate(fd, newsize)) { \
+		err("could not resize file"); \
+		goto warning; \
+	} \
+ \
+	return TRUE; \
+ \
+ warning: \
+	return err("ELF file may have been corrupted!"); \
+}
+
+
+/* First elements of Elf32_Ehdr and Elf64_Ehdr are common.
 */
-static int readelfheader(int fd, Elf_Ehdr *ehdr)
+static int readelfheaderident(int fd, Elf32_Ehdr *ehdr)
 {
 	errno = 0;
-    if (read(fd, ehdr, sizeof *ehdr) != sizeof *ehdr)
+	if (read(fd, ehdr, EI_NIDENT) != EI_NIDENT)
 		return ferr("missing or incomplete ELF header.");

 	/* Check the ELF signature.
@@ -70,89 +324,48 @@ static int readelfheader(int fd, Elf_Ehdr *ehdr)
 		  ehdr->e_ident[EI_MAG1] == ELFMAG1 &&
 		  ehdr->e_ident[EI_MAG2] == ELFMAG2 &&
 		  ehdr->e_ident[EI_MAG3] == ELFMAG3))
-        return err("missing ELF signature.");
+	{
+		err("missing ELF signature.");
+		return -1;
+	}

 	/* Compare the file's class and endianness with the program's.
 	 */
-    if (ehdr->e_ident[EI_DATA] != ELF_DATA)
-        return err("ELF file has different endianness.");
-    if (ehdr->e_ident[EI_CLASS] != ELF_CLASS)
-        return err("ELF file has different word size.");
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+	if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB) {
+		do_reverse_endian = 0;
+	} else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) {
+/* 		fprintf(stderr, "ELF file has different endianness.\n"); */
+		do_reverse_endian = 1;
+	}
+#elif __BYTE_ORDER == __BIG_ENDIAN
+	if (ehdr->e_ident[EI_DATA] == ELFDATA2LSB) {
+/* 		fprintf(stderr, "ELF file has different endianness.\n"); */
+		do_reverse_endian = 1;
+	} else if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) {
+		do_reverse_endian = 0;
+	}
+#else
+#error unkown endianness
+#endif
+	else {
+		err("Unsupported endianness");
+		return -1;
+	}

 	/* Check the target architecture.
 	 */
-    if (ehdr->e_machine != ELF_ARCH)
-        return err("ELF file created for different architecture.");
-
-    /* Verify the sizes of the ELF header and the program segment
-     * header table entries.
-     */
-    if (ehdr->e_ehsize != sizeof(Elf_Ehdr))
-        return err("unrecognized ELF header size.");
-    if (ehdr->e_phentsize != sizeof(Elf_Phdr))
-        return err("unrecognized program segment header size.");
-
-    /* Finally, check the file type.
-     */
-    if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
-        return err("not an executable or shared-object library.");
-
-    return TRUE;
+/*	 if (EGET(ehdr->e_machine) != ELF_ARCH) { */
+/* 		/\* return err("ELF file created for different architecture."); *\/ */
+/* 		fprintf(stderr, "ELF file created for different architecture.\n"); */
+/* 	} */
+	return ehdr->e_ident[EI_CLASS];
 }

-/* readphdrtable() loads the program segment header table into memory.
- */
-static int readphdrtable(int fd, Elf_Ehdr const *ehdr, Elf_Phdr **phdrs)
-{
-    size_t      size;

-    if (!ehdr->e_phoff || !ehdr->e_phnum)
-        return err("ELF file has no program header table.");
+HEADER_FUNCTIONS(32)

-    size = ehdr->e_phnum * sizeof **phdrs;
-    if (!(*phdrs = malloc(size)))
-        return err("Out of memory!");
-
-    errno = 0;
-    if (read(fd, *phdrs, size) != (ssize_t)size)
-        return ferr("missing or incomplete program segment header table.");
-
-    return TRUE;
-}
-
-/* getmemorysize() determines the offset of the last byte of the file
- * that is referenced by an entry in the program segment header table.
- * (Anything in the file after that point is not used when the program
- * is executing, and thus can be safely discarded.)
- */
-static int getmemorysize(Elf_Ehdr const *ehdr, Elf_Phdr const *phdrs,
-                         unsigned long *newsize)
-{
-    Elf_Phdr const     *phdr;
-    unsigned long       size, n;
-    size_t              i;
-
-    /* Start by setting the size to include the ELF header and the
-     * complete program segment header table.
-     */
-    size = ehdr->e_phoff + ehdr->e_phnum * sizeof *phdrs;
-    if (size < sizeof *ehdr)
-        size = sizeof *ehdr;
-
-    /* Then keep extending the size to include whatever data the
-     * program segment header table references.
-     */
-    for (i = 0, phdr = phdrs ; i < ehdr->e_phnum ; ++i, ++phdr) {
-        if (phdr->p_type != PT_NULL) {
-            n = phdr->p_offset + phdr->p_filesz;
-            if (n > size)
-                size = n;
-        }
-    }
-
-    *newsize = size;
-    return TRUE;
-}
+HEADER_FUNCTIONS(64)

 /* truncatezeros() examines the bytes at the end of the file's
 * size-to-be, and reduces the size to exclude any trailing zero
@@ -185,97 +398,20 @@ static int truncatezeros(int fd, unsigned long *newsize)
 	return TRUE;
 }

-/* modifyheaders() removes references to the section header table if
- * it was stripped, and reduces program header table entries that
- * included truncated bytes at the end of the file.
- */
-static int modifyheaders(Elf_Ehdr *ehdr, Elf_Phdr *phdrs,
-                         unsigned long newsize)
-{
-    Elf_Phdr *phdr;
-    size_t    i;
-
-    /* If the section header table is gone, then remove all references
-     * to it in the ELF header.
-     */
-    if (ehdr->e_shoff >= newsize) {
-        ehdr->e_shoff = 0;
-        ehdr->e_shnum = 0;
-        ehdr->e_shentsize = 0;
-        ehdr->e_shstrndx = 0;
-    }
-
-    /* The program adjusts the file size of any segment that was
-     * truncated. The case of a segment being completely stripped out
-     * is handled separately.
-     */
-    for (i = 0, phdr = phdrs ; i < ehdr->e_phnum ; ++i, ++phdr) {
-        if (phdr->p_offset >= newsize) {
-            phdr->p_offset = newsize;
-            phdr->p_filesz = 0;
-        } else if (phdr->p_offset + phdr->p_filesz > newsize) {
-            phdr->p_filesz = newsize - phdr->p_offset;
-        }
-    }
-
-    return TRUE;
-}
-
-/* commitchanges() writes the new headers back to the original file
- * and sets the file to its new size.
- */
-static int commitchanges(int fd, Elf_Ehdr const *ehdr, Elf_Phdr *phdrs,
-                         unsigned long newsize)
-{
-    size_t      n;
-
-    /* Save the changes to the ELF header, if any.
-     */
-    if (lseek(fd, 0, SEEK_SET))
-        return ferr("could not rewind file");
-    errno = 0;
-    if (write(fd, ehdr, sizeof *ehdr) != sizeof *ehdr)
-        return err("could not modify file");
-
-    /* Save the changes to the program segment header table, if any.
-     */
-    if (lseek(fd, ehdr->e_phoff, SEEK_SET) == (off_t)-1) {
-        err("could not seek in file.");
-        goto warning;
-    }
-    n = ehdr->e_phnum * sizeof *phdrs;
-    if (write(fd, phdrs, n) != (ssize_t)n) {
-        err("could not write to file");
-        goto warning;
-    }
-
-    /* Eleventh-hour sanity check: don't truncate before the end of
-     * the program segment header table.
-     */
-    if (newsize < ehdr->e_phoff + n)
-        newsize = ehdr->e_phoff + n;
-
-    /* Chop off the end of the file.
-     */
-    if (ftruncate(fd, newsize)) {
-        err("could not resize file");
-        goto warning;
-    }
-
-    return TRUE;
-
-  warning:
-    return err("ELF file may have been corrupted!");
-}
-
 /* main() loops over the cmdline arguments, leaving all the real work
 * to the other functions.
 */
 int main(int argc, char *argv[])
 {
 	int				fd;
-    Elf_Ehdr            ehdr;
-    Elf_Phdr           *phdrs;
+	union {
+		Elf32_Ehdr	ehdr32;
+		Elf64_Ehdr	ehdr64;
+	} e;
+	union {
+		Elf32_Phdr	*phdrs32;
+		Elf64_Phdr	*phdrs64;
+	} p;
 	unsigned long	newsize;
 	char			**arg;
 	int				failures = 0;
@@ -283,7 +419,8 @@ int main(int argc, char *argv[])
 	if (argc < 2 || argv[1][0] == '-') {
 		printf("Usage: sstrip FILE...\n"
 			   "sstrip discards all nonessential bytes from an executable.\n\n"
-               "Version 2.0 Copyright (C) 2000,2001 Brian Raiter.\n"
+			   "Version 2.0-X Copyright (C) 2000,2001 Brian Raiter.\n"
+			   "Cross-devel hacks Copyright (C) 2004 Manuel Novoa III.\n"
 			   "This program is free software, licensed under the GNU\n"
 			   "General Public License. There is absolutely no warranty.\n");
 		return EXIT_SUCCESS;
@@ -301,14 +438,29 @@ int main(int argc, char *argv[])
 			continue;
 		}

-        if (!(readelfheader(fd, &ehdr)                  &&
-              readphdrtable(fd, &ehdr, &phdrs)          &&
-              getmemorysize(&ehdr, phdrs, &newsize)     &&
+		switch (readelfheaderident(fd, &e.ehdr32)) {
+			case ELFCLASS32:
+				if (!(readelfheader32(fd, &e.ehdr32)					&&
+					  readphdrtable32(fd, &e.ehdr32, &p.phdrs32)		&&
+					  getmemorysize32(&e.ehdr32, p.phdrs32, &newsize)	&&
 					  truncatezeros(fd, &newsize)						&&
-              modifyheaders(&ehdr, phdrs, newsize)      &&
-              commitchanges(fd, &ehdr, phdrs, newsize)))
+					  modifyheaders32(&e.ehdr32, p.phdrs32, newsize)	&&
+					  commitchanges32(fd, &e.ehdr32, p.phdrs32, newsize)))
 					++failures;
-
+				break;
+			case ELFCLASS64:
+				if (!(readelfheader64(fd, &e.ehdr64)					&&
+					  readphdrtable64(fd, &e.ehdr64, &p.phdrs64)		&&
+					  getmemorysize64(&e.ehdr64, p.phdrs64, &newsize)	&&
+					  truncatezeros(fd, &newsize)						&&
+					  modifyheaders64(&e.ehdr64, p.phdrs64, newsize)	&&
+					  commitchanges64(fd, &e.ehdr64, p.phdrs64, newsize)))
+					++failures;
+				break;
+			default:
+				++failures;
+				break;
+		}
 		close(fd);
 	}